TECHNOLOGIES

In this section you can learn more about the technologies Sound Temple use. For ease of navigation this guide has been split into multiple pages and you can jump to a topic that interests you by clicking the links below.

• Introduction
• Electronic Signal Generation
• Digital Audio Signal Generation
• Sample Rate
• Bit Depth
• Digital and Analogue Audio Signal Manipulation
• Digital Audio Mastering
• Clip Removal
• Volume Control
• Panning
• Normalisation
• Compression
• Limiting
• Expansion
• Noise Gates

Panning

Panning is the vectoring of gain through a stereo image. Panning, or stereo re-adjustment is important for mastering. If a certain instrument is placed too far left of right an impression of non-reality will be experienced. If an instrument is processed with a stereo effect and played on a mono aural rendering device, the instrument may be lost. This effect can often be heard in a nightclub or large public house. A track appears to lose a certain instrument, as it spaced too far to one side of the stereo image.

Normalisation

To normalize a file means to raise its volume so that the highest-level sample in the file reaches a maximum level. This function fully utilises the dynamic range of a 16-bit (or higher) register. This is helpful for making multiple waveforms perceptually as loud as each other. This is an essential mastering process as all tracks on a compact disc will need to be at the same level. As stated, for every 6 db below 0 db only 15 of the possible 16 bits are being used. The dynamic range will be compromised if normalisation is not applied.

Compression

Compression decreases the volume of high amplitude signals whilst at the same time increasing the gain of low amplitude sounds. The result is a more even volume level. Compression may be expressed mathematically by the following equation:

signal_out (t) = signal_in (t) * (abs (signal_in (t))) ^ A

When A = -1, all dynamics should be removed, when A= 0 there is no effect and when A > 0 the dynamics are heightened. As A increases the greater the distortion. Distortion can be achieved this way.

Compression is applied to almost all radio stations and most pop music (to a lesser extent) so that your stereo is not damaged by transient signals. Compression is very useful when recording vocals so that the artist does not have to sing at the same volume all the time. Compression is also however, an essential part of the mastering chain of processes. It is essential to recognise that commercial music recorded at a state of the art studio will be listened to on a variety of playback devices. These range from a small transistor radio to a professional monitoring system. It is therefore important to ensure that as much of the original signal is processed into a bandwidth that is ubiquitous to all playback devices. Compression is used for this very purpose.

The compressor setting is usually stated as a ratio, such as 2:1, which means that the input level would have to increase by two decibels to create a one decibel increase in the output. With a 4:1 setting, the input would need to change by 4 dB for a 1 dB change in the output level, and so on. A compressor's input/output relationship is often described by a simple graph, as in figure 2.4.6. The horizontal axis corresponds to the input signal level, and the vertical axis is the output level (both measured in decibels). A line at 45 degrees corresponds to a gain of one - any input level is mapped to exactly the same output level.

The compressor changes the slope (makes it more horizontal) of that line above some value called the threshold (which is most often adjustable). The height of the line defines the dynamic range of the output, and the slope of that line is the same as the compressor's gain. A Noise gate should be used with the compressor, since the compressor will amplify background noise when there is no foreground signal. Figure 2.4.6 and figure 2.4.6.1 show a typical compressor.